1. Field of the Invention
The invention relates to an electric pump unit that is used as a hydraulic pump that supplies hydraulic pressure to, for example, a transmission of a motor vehicle.
2. Discussion of Background
Hydraulic pressure is supplied to a transmission of a motor vehicle by a hydraulic pump. In a motor vehicle in which so-called idling stop is performed, that is, an engine is stopped when the vehicle stops to save energy, an electric hydraulic pump is used to supply hydraulic pressure to a transmission even during idling stop.
Since an electric hydraulic pump for a transmission of a motor vehicle is installed in a limited space in a vehicle body, size reduction of the electric hydraulic pump is required. In addition, weight reduction and cost reduction are also required. To meet these requirements, Japanese Patent Application Publication No. 2008-215088 (JP 2008-215088 A) describes an electric pump unit in which a pump, a pump-driving electric motor and a controller for the electric motor are installed in a single unit housing.
In such a conventional electric pump unit, a motor housing is connected to a pump body that constitutes the pump, and the electric motor and the controller are installed in a sealed motor chamber that is formed in the motor housing. The electric motor is disposed at a position on a pump body side in the motor chamber, and a substrate of the controller is fixed to an end face of the electric motor, which is on the opposite side of the electric motor from to the pump body. In addition, multiple electric and electronic components, such as a capacitor, a FET (Field Effect Transistor), which constitute the controller are attached to the substrate.
The electric pump unit for a motor vehicle is disposed in an engine room of the motor vehicle. Due to heat produced at the stator coils of the electric motor, the temperature of the electric motor and the temperature in the motor chamber increase, and the temperatures of components of the controller in the motor chamber also increase.